Then draw three parallel lines in directions that are not parallel to the horizontal and vertical directions. These three parallel lines have 3*7=2 1 intersection points with the above seven straight lines. Ensure that intersections do not overlap.
So ten straight lines have thirty-one intersections.
It can be understood that
3 1=9+8+7+6+ 1
The first six straight lines intersect at 1, and the other four straight lines intersect with the previous one.